1. Field of the Invention
The present invention relates to a double floor or double bottom for removing air from rooms, particularly clean rooms, which are connected to the air supply system of a ventilating and/or air-conditioning unit. The present invention particularly relates to a double floor in which the upper floor plane is formed by perforated plates with holes and/or slots. The perforated plates are supported by support members. On the underside of the perforated plates is provided a stiffening system composed of stiffening webs, stiffening sections or the like.
2. Description of the Related Art
When double floors of the above-described type are used in rooms, particularly clean rooms, large quantities of air are conducted vertically from the top into the room and are subsequently drawn off from below through the double floor.
The air flow is laterally deflected in the double floor underneath the perforated plates and is drawn off from the double floor at one or more sides of the room.
When air is conducted through the room in this manner, it is particularly important to achieve a distribution of the air which is as uniform as possible over the entire cross-sectional area of flow within the room. Such a uniform distribution can be achieved when the space within the double floor, i.e., underneath the perforated plates, can be dimensioned sufficiently high or when the free cross-sectional area of the double floor is very small.
Experience has shown that a uniform distribution can be achieved when the free cross-sectional area of the area of passage through the double floor corresponds approximately to the cross-sectional area available for moving the air from the double floor area.
The air flow can also be made uniform within certain limits by providing different free cross-sectional areas in the perforated plates, particularly by varying or differently arranging the shape, size, location or arrangement of the holes and/or slots in the perforated plates.
The reduction of the free cross-sectional area is limited by the pressure losses in the floor. However, such pressure losses are undesirable because they lead to an increase in energy costs. For example, a pressure loss of 200 Pa in the double floor already corresponds to a power of approximately 90 W/m.sup.2.
It is, therefore, the primary object of the present invention to provide a double floor of the above-described type in which a uniform distribution of the air drawn off over the surface of the double floor is achieved while the pressure loss is low to average.